Infrared radiation detectors have gained wide acceptance as non-contact temperature detectors. Such detectors have been used in such widespread applications as detecting heat loss from insulated structures, detecting electrical faults which result in increased temperature, and detecting ear temperatures of patients.
A preferred radiation detector is a thermopile. A thermopile generates a voltage which is indicative of the difference between hot and cold junction temperatures, the hot junction temperature being dependent on the heat flux from a target surface viewed by the hot junction. The heat flux is proportional to the difference in temperatures of the target and thermopile raised to the fourth power.